Squeeze beneath a horse: it makes gelding niggled (7)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

So how does gelding become niggled? ANAGRAM it. Additionally, it’s RAM for squeeze (into a confined space) below A NAG or horse. With the previous clue’s references fresh in mind, I rather thought a gelding would be less niggled by such squeezing than a stallion.